They have learned and apparently have taken constructive actions.
Here is the reply  from [log in to unmask]:
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Thank you for your recent email.
 
The RSPCA very much regrets the unnecessary killing of Boe, the stray
ferret collected from Whitchurch Police Station.  It is certainly not
normal practice to euthanase healthy animals.  Our usual procedures were
not followed on this occasion and one of the learning points from this bad
experience has been to reinforce those procedures for all concerned.
 
We do not discriminate against ferrets or any other creature in any way
when allocating resources.  During the month of April, for example, in
South Wales we had over thirty ferrets in care awaiting rehoming.
 
The RSPCA provides a round the clock collection service for animals in
need.  Last year in Wales we collected over eleven thousand animals in this
way.  The majority of these creatures, being injured or poorly, are taken
to veterinary surgeons.  Some, on account of their condition are put to
sleep, others are rehabilitated and either rehomed or returned to the wild.
The sheer volume of animals that we deal with means that not only are our
resources often at full stretch but also those of the individuals and other
organisations that assist us in our work.  Over recent months we have
increased our collection service and we are continuing to make developments
in this area.
 
Please be assured that our officers work extremely hard to protect animals
and we shall continue to strive to meet the high standards on which the
reputation of the Society is built.
 
Thank you for taking the trouble to write and for allowing us the
opportunity to make this explanation.
 
Kind regards,
 
RSPCA Enquiries Service
 
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Perhaps folks in the British ferret groups can find ways to work with the
RSPCA in some locations where that isn't done yet?  Here in some places
the local general humane groups are very interested in working with people
and learning, but in others the local branches/ local general shelters are
anything but...
[Posted in FML issue 3061]